The rapid pace of discovery in the life sciences requires that we constantly examine and improve the ways in which we prepare graduate students for productive careers. In response to these recent developments, the current Training Program in Molecular, Cellular, and Chemical Biology (MCCB) has been substantially reconfigured in this proposal and is, in essence, a new program. Intended to provide an even more comprehensive and interactive training experience for students interested in research and discovery in the life sciences, this new curriculum includes a broad array of established and emerging disciplines in the life sciences, ranging from genetics and evolutionary biology, to systems and chemical biology, to molecular biology and neurobiology. The new Joint Training Program in Molecules, Cells and Organisms (MCO) represents the combined talents of faculty from Molecular & Cellular Biology, Chemistry and Chemical Biology, and Organismic and Evolutionary Biology at Harvard. We believe that the application of the tools of molecular biology and genomics to virtually every discipline, from evolutionary biology, to cell biology, biochemistry and biophysics has revealed a complexity of organization and function that few could have dreamed of 20 years ago. This training will involve an initial exposure to a broad sweep of fundamental problems at every level through a set of core courses, followed by in depth immersion in focused areas. The latter will be accomplished through additional course work and Ph.D. thesis research. The newly designed group of core courses, in-depth track requirements, quantitative training, and specialized nanocourses combine to provide a strong foundation from which trainees will go on to conduct laboratory research in an exciting, interactive, and supportive environment. The MCO Training Program is precisely the kind of initiative that will advance the science of the post-genomic era, as the collective attention of the life science community turns toward the daunting task of elucidating the function of genes and their roles in the vast physiological networks necessary to develop and maintain complex organisms. RELEVANCE (See instructions): The proposed training program is designed to provide both the breadth and depth of didactic and research training necessary to prepare life scientists for a new era of interdisciplinary and collaborative research.